Dry-seal pressure-type gasholders provided with stretch resistant seal structures and tensioned fender structures



March 25, 1969 H. WIGGINS 3,434,815

DRY-SEAL PRESSURE-TYPE GASHOLDERS PROVIDED WITH STRETCH RESISTANT SEALSTRUCTURES AND TENSIONED FENDER STRUCTURES Filed Feb. 15. 1965 Sheet Iof 2 INVENTOR. t 7 JOHN H. W/GG/NS u {2 p3 gg w AT TOP/VEVS March 25,1969 J. H. WlGGlNS 3,

-TYPE GASHOLDERS PROVIDED WITH STRETCH DRY-SEAL PRESSURE RESISTANT SEALSTRUCTURES AND TENSIONED FENDER STRUCTURES Filed Feb. 15, 1965 INVENTOR.JOHN H W/GG/NS 645/4? ATTORNEYS United States Patent ABSTRACT OF THEDISCLOSURE Gasholder of the type having an annular side wall and apiston disposed therein with a curtain seal connected between the sidewall and a smooth and tensioned and sinuous backstop surface mounted onthe piston, the sinuous backstop surface having an effectivecircumference less than that of the inner surface of the side wall andthe curtain seal having an initial effective circumference intermediatethat of the side wall and the sinuous backstop surface.

This invention relates to d1y-seal, piston-type gasholders and otherfluid storage apparatus, of the particular type or kind that comprise acontainer provided with a cylindrical side wall, a vertically movablepiston in the container that forms the top wall of the gas storage spaceof the apparatus, a seal for the space between the piston and thecontainer side wall made of gas-tight fabric and constructed in the formof a flexible curtain suspended between .and attached to the piston andto the container side wall and proportioned so as to provide for therise and fall of the piston, and back up members or abutment surfacesdisposed in such relationship with the curtain-like fabric seal thatduring the cycle of operations of the piston the abutment surfacesfunction as back stops that absorb pressure exerted on the seal by thegases confined in the storage chamber of the apparatus. Generally theportion of the container side wall located above the point where thefabric seal is attached to the wall is used to constitute an outer backstop that is located at the outer edge of the seal and which absorbspressures exerted on the seal during the upward stroke of the piston,and at least one vertically movable inner back stop or abutment memberof tubular or cylindrical form is arranged inside of the outer back stopin spaced, concentric relation with the same so as to absorb pressureexerted on the fabric seal during the downward stroke of the piston. Ifthe fabric seal is constructed in the form of a relatively long or deepcylinder attached at one of its ends to the outer back stop formed bythe container side wall and attached at its other end to the piston, theinner back stop will be formed by a tubular or cylindrical memberrigidly combined with the piston and projecting upwardly from the same,and if the fabric seal is composed of two cylindrical sections, one ofwhich is attached to the container side wall and the other attached tothe piston, an additional vertically movable back stop of tubular orcylindrical form will be arranged between the piston and the containerside wall and attached to the two sections of the seal in such a waythat during the cycle of operations of the piston the additional backstop will coact with the back stop on the piston to back up the innerseal section (the one nearest the piston), and the additional back stopwill coact with the abutment surface on the container side wall to backup the outer section of the seal (the one nearest the container wall),as disclosed in US. Patent No. 2,606,824, dated Aug. 12, 1952, to JohnW. Allen.

This type of gasholder with one outer and one inner back stop is shownin the prior patent to Wiggins, et al.

No. 2,723,908, and the instant invention is an improvement over thegasholders shown therein.

I have discovered that the proportioning of the circumference of theouter back stop and the inner back stop as described in the above patentis in error because making the inner back stop of the same effectivecircumference as the outer back stop will place the seal under tensionsubstantially at all times so as to effect a permanent stretch to alength equal to the length of the outer back stop. Such lengthening ofthe seal due to undue stretching will, in a comparatively short time,result in the seal forming deleterious wrinkles which will materiallyreduce the life of the seal.

I have discovered that a proper proportioning of the effective length ofthe outer back stop to the effective length of the inner back stop inrelation to the relaxed circumferential length of the seal will resultin creating alternate compressions and tensions and thereby offset apermanent growth by a permanent compression of the seal and henceprevent such deleterious wrinkles. in normal operation, the seal will beheld against the outer back stop about the same number of days per yearas it is held against the inner back stOp and this invention utilizes along time held compression effect to counter-act a long time heldtension effect. It is necessary to maintain a portion of the gap as aseal compressing portion as well as to maintain the other portion of thegap as a seal tensioning portion to reduce undue permanent lengthening,and I have found that if the percentage compressibility of a new sealfor this type of gasholder is more than 2% of the circumferential seallength, then if the designed compression is held to less than 1%, theoperation is a safe one to extend the operational life expectancy of aseal without deleterious wrinkles.

One object of the invention therefore is to proportion thecircumferential length of this seal and the effective cylindrical lengthof a scalloped back stop surface or inner back stop in such a way thatthere will always be some percentage of compression of the seal when itis pressed against the inner back stop after a long period of service.

Another object of the invention is to provide an improved sinuoussurface to constitute the inner back stop which will prevent anywrinkling when the seal is against this surface.

A further object of the invention is to provide an inner back stopcomprising specially constructed and mounted plates so that the loads onthe (plates and the means for joining the plates will be resisted in theplates and the means as tension.

A further object of the invention is to mount these scalloped plates sothat all the plates are identical and hence the plate tensions balanceeach other all around.

Still another object of the inventionis to so design the steel plates ofsinuous or corrugated structure and so that the attachments of the seallplates to each other are in completely accessible locations and can beperformed by one man.

A further object of the invention is to provide a piston structure whichfacilitates the assembly of the posts and the plates in accuratepredetermined positions.

The above and other objects of the invention are attained as describedin connection with a preferred embodiment thereof, as disclosed in theaccompanying drawings in which:

FIGURE 1 is a horizontal sectional view taken in the plane indicated bythe line 11 in FIG. 3;

FIG. 2 is a fragmentary elevational view taken as generally indicated bythe line 2-2 in FIG. 1;

FIG. 3 is a vertical sectional view taken as indicated by the line 3--3in FIG. 2;

FIG. 4 is an enlarged portion of the section shown in FIG. 3;

FIG. 5 is a fragmentary perspective view illustrating the rolling of theseal in a loop as it moves from the inner back stop to the outer backstop or vice versa;

FIG. 6 is a fragmentary sectional view taken as indicated with the line66 in FIG. 2; and

FIG. 7 is an elevational view of the fragmentary sectional view shown inFIG. 6 as viewed from the right thereof.

The gasholder of the present invention includes a cylindrical side wall11, a bottom 12 and a roof, not shown, to form a completely enclosedcontainer for a dryseal piston-type gasholder. There is provided apiston 13 having a solid bottom wall 14 around which a circular angle orgirder 16 is mounted and above which a circular framework is providedincluding vertical posts 17 and an upper circular angle or girder 18.The circular girder 18 has respective depending lugs 19 welded theretowhich have a pair of apertures to receive fastening bolts (unnumbered)for the vertical posts 17 which at their bottoms are welded to brackets20 extending upwardly from their welded connections to the bottom wall14 of the piston 13. This circular framework comprises the first part ofthe inner back stop.

A rubberized fabric seal 21 is provided and is secured about theperiphery of the circular girder 16 by a series of clamp bars 2 2 boltedto the girder 16, and, at its upper end, the seal 21 is secured by aseries of clamp bars 23 to the side wall 11 of the gasholder. At bothpoints of the attachment of the seal 21 to the piston 13 and to the sidewall 11, care is taken to make the connection gas-tight. The seal 21itself is a rubberized fabric of gastight character.

Of special interest is the construction and character of the outer wallof the piston 13 which forms the second part of the inner back stop forthe seal 21. This outer wall is made up of a series of limber plates 26which are constructed to provide a smooth continuous scalloped orsinuous surface at the outer edge of the piston 13. The curved ridges26a of this surface extend vertically so that a vertically corrugatedsurface is presented as a back stop to the seal 21 and this is of asmooth continuous character. It will be seen that each plate 26 has itscurved ridge 26a seated over one of the vertical posts 17 and thenextends inwardly therefrom in concave fashion and the two edges of eachplate 26 are provided with a right angle flange 27 which extendsvertically and directed toward the center of the piston 13. The flanges27 of adjacent plates 26 are secured together by a plurality of bolts28, the dimensioning of the plates and the spacing of the posts 17 beingsuch that these plates 26 are in tension when bolted together andcorrespondingly, the bolts 28 are also in tension. No gap is presentwhere the edges of the plates 26 meet, and therefore the seal 21 liessmoothly as it crosses these edges. In effect therefore a smoothcontinuous corrugated or sinuous surface is presented as an inner backstop for the seal 21 and this surface including the corrugations has anaverage diameter of the circle C-3 which is shown in phantom lines inFIG. 4. This circle 0-?) may be substantially equal to or slightly less(as shown) than the circle C4 of the relaxed condition of the seal 21,i.e., when there is no gas present in the gasholder. Rectangular washers30 are provided for each of the bolts 28.

It is seen therefore that the circumferential length of the fabric seal21 when relaxed is less than the circumferential length of the outerback stop or gasholder side wall 11, and is greater than the effectivecircumferential length of the sinuous support or second part of theinner back stop carried by the piston 13. Therefore when the seal 21 ispressed against the gasholder side wall 11 (C-1) it will be undertension and a certain amount of stretch will occur, and correspondingwhen the seal 21 is pressed against the inner back stop (C-2) it will beunder a slight compression and a counteraction of the stretching willoccur. This combination of alternate compression and tension of the seal21 as the cycles of the piston 13 continue prevents a permanentlengthening of the seal 21 and allows no wrinkling of the seal 21 asoccurs if it were continually under tension and continually stretched.By properly proportioning the circumferential length (C4) of the seal 21and the effective circumferential length (C-3) of the scalloped orsinuous surface formed by the plates 26, there will always be somepercentage of compression in the seal 21 when it is pressed against thesinuous part of the inner back stop and this compression will counteractthe effect of a comparable percentage of tension when the seal 21 ispressed against the outer back stop after a similar period of service.

The desirable optimum condition is to have the compression effect in theshortening of the seal 21 balance the tension effect in the lengtheningof the seal 21 so that additional years of wrinkle-free operation areprovided. Referring to FIG. 4 there is shown a gap G between the innersurface of the outer side wall 11 of the gasholder and the outer sufraceof the piston 13 and this gap is termed the operational gap in which theseal 21 must work as the piston 13 rises and falls within the gasholder.There is also indicated a second radial distance Gc, called the sealcompression gap, which is the radial distance from the relaxed positionof the seal 21 to the effective circumference of the scalloped back stopsurface and, roughly, this compression gap Gc should be an amount whichis essential for the allowable compression of the seal 21 duringoperation of the gasholder. In general the circumference (C4) of theseal 21 is madeslightly greater than the effective circumference (C3) ofthe scalloped back stop. When the seal 21 is relaxed, there is a thirdradial distance Gt extending radially outward from the seal 21 to theinner wall 11 of the gasholder and this gap constitutes a seal tensiongap, and G! is an amount which is essential for the desired stretch ofthe seal 21 during the operation of the gasholder to balance thecompression of the seal 21.

The construction of the sinuous inner back stop provides severaladvantages. In the first place it presents the convex surfaces of thevertically disposed plates 26 inwardly in order that the loads of theseal 21 may be resisted as tension. Also the plates 26 are so joinedthat each plate 26 balance the tensions in the two adjacent plates 26,and therefore there is balanced tension in all the plates 26. Thisbalanced tension transmits only radially directed forces to thesupporting frame posts 17 around which the plates 26 are mounted.

In assembly, the vertical seams of the plates 26 are completelyaccessible inside of the piston 13 and can be set in place by one man inan unobstructed area. Also in assembling these plates 26, they aretemporarily supported by the bolts at the top of the posts 17 by thesimple swingable attachment at each post 17 by means of a bolt 17a; andas the plates 26 are progressively joined at their vertical flanges 27these flanges 27 are automatically pulled into vertical lines so thatthey fit controlled by the level line of the holes in the posts 17 forthe bolts 17a. This removes the necessity for the posts 17 to beperfectly plumb. The only necessary accurate location for spacing of theposts 17 is at their top connections to the circular girder 18.

In operation, the construction of the sinuous part of the inner backstop is smooth and uninterrupted without any unsupported seal area, asfound for example in a full length vertical solt into which the seal 21might stretch out of control, and also, this smooth continuous surfaceinduces the seal 21 to compress instead of wrinkling as every tiny areaof the seal 21 is pressed against the back stop surface by the gas inthe gasholders.

While I have shown and described a preferred embodiment of theinvention, it is apparent that the invention is capable of variation andmodification from the form shown so that the scope thereof shall belimited only by the scope of the claims appended hereto.

I claim:

1. A gasholder comprising a substantially vertical cylindrical sidewall, a vertically movable cylindrical piston therein spaced from saidside wall, an annular flexible seal secured along one edge thereof insealed relation to said side wall along a circular line intermediate theheight thereof and secured along the other edge thereof in sealedrelation to said piston along a circular line adjacent to the bottomthereof, and an annular fender structure mounted on said piston andextending upwardly therefrom and spaced from said side Wall, said fenderstructure including a series of vertical circumferentially spaced postsmounted in a circular array on said piston, and a series of plates eachhaving at least one vertically disposed smooth ridge disposed adjacentto one of said posts and having arcuate concave sections disposed oneach side thereof, and means joining the adjacent vertical edges of saidplates to provide a continuous sinuous outer surface for said fenderstructure, said outer surface being smooth and continuous at the ridgesdisposed at said posts and being smoothly concave between said ridgesand across the junctures between adjacent plates.

2. The gasholder set forth in claim 1, wherein said plates are undertension whereby to urge said concave surfaces outwardly with respect tosaid piston.

3. The gasholder set forth in claim 1, wherein each of said plates hasinwardly directed flanges on the vertical edges thereof, and said meanssecuring said adjacent plates is a series of bolts holding said platesin tension.

4. A gasholder comprising a substantially vertical cylindrical sidewall, a vertically movable cylindrical piston therein spaced from saidside wall, an annular flexible seal secured along one edge thereof insealed relation to said side wall along a circular line intermediate theheight thereof and secured along the other edge thereof in sealedrelation to said piston along a circular line adjacent to the bottomthereof, and an annular fender structure mounted on said piston andextending upwardly therefrom and spaced from said side wall, said fenderstructure including a series of vertical circumferentially spaced postsmounted on a circular array on said piston, a series of plates eachhaving at least one vertically dis posed smooth ridge disposed adjacentto one of said posts and having arcuate concave sections disposed oneach side thereof, means joining the adjacent vertical edges of saidplates to provide a continuous sinuous outer surface for said fenderstructure, said outer surface being smooth and continuous at the ridgesdisposed at said posts and being smoothly concave between said ridgesand across the junctures between adjacent plates, the effective diameterof the outer surface of said fender structure be ing less than theeffective diameter of the inner surface of said side wall, said annularflexible seal having a normal and unstretched effective diameterintermediate that of the outer surface of said fender structure and theinner surface of said side wall, whereby the pressure of the gas in saidgasholder urges said seal against the inner surface of said side wall toplace said seal in tension when said piston is in the upper portion ofthe travel thereof and the pressure of the gas in said gasholder urgessaid seal against the outer surface of said fender structure to placesaid seal under compression when said piston is in the lower portion ofthe travel thereof, thereby alternately to place said seal under tensionand compression as said piston moves with respect to said side wall andthus to prevent excessive permanent lengthening of the seal and toprevent wrinkling of the seal in use.

5. A gasholder comprising a substantially vertical cylindrical sidewall, a vertically movable cylindrical piston therein spaced from saidside wall, an annular flexible seal secured adjacent to one edge thereofin sealed relation to said side wall along a circular line intermediatethe height thereof and secured adjacent to the other edge thereof insealed relation to said piston along a circular line, and an annularfender structure mounted on said piston and extending upwardly therefromand spaced from said side wall, the outermost portions of said pistonand said fender structure lying within a cylindrical surface spaced fromsaid side wall a predeterined distance to provide an operational gaptherebetween, said fender structure including an outer sinuous surfacehaving an effective diameter less than the inner diameter of said sidewall but greater than said cylindrical surface while maintaining saidoperational gap, said annular flexible seal having a normal andunstretched diameter intermediate that of the inner surface of said sidewall and said cylindrical surface, whereby the pressure of the gas insaid gasholder urges said seal against the inner surface of said sidewall to place said seal in tension when said piston is in the upperportion of the travel thereof, and whereby the pressure of the gas insaid gasholder urges said seal against the outer surface of said fenderstructure to place said seal under compression when said piston is inthe lower position of the travel thereof, thereby alternately to placesaid seal under tension and compression as said piston moves withrespect to said side wall and thus toprevent excessive permanentlengthening of the seal and to prevent wrinkling of the seal in use.

6. The gasholder set forth in claim 5, wherein said flexible seal isformed of a rubberized fabric.

7. The gasholder set forth in claim 5, wherein said fender structureincludes a series of vertical circumferentially spaced posts mounted ina circular array on said piston, and a series of plates mounted on saidposts and providing vertically extending concave surfaces between saidposts.

References Cited UNITED STATES PATENTS 11/1955 Wiggins et a1. 48l78 2/1954 Perkins 52245

